Chapter 3

Supplementary Components and Systems

“Introduction to Modern Power Electronics”, 2nd Ed., John Wiley 2010by

Andrzej M. Trzynadlowski

Chapter 3 2

Driver for an SCR with transformer isolation

Fig. 3.1

SCR

PTR

D2

D1

DZ

(+)

TRA

Chapter 3 3

Optically isolated driver for an SCR

Fig. 3.2

SCR

LED

LAT

OPTO-COUPLER

Chapter 3 4

Non-isolated driver for a triac

Fig. 3.3

TR IA C

(+ )

TRA

Chapter 3 5

Optically isolated driver for a triac

Fig. 3.4

TRIAC

LAT

OPTO-COUPLER

R

LED

Chapter 3 6

Driver for a GTO with transformer isolation

Fig. 3.5

SCR

PTR

DZ

RCT

GT O

M1 M2

LC

(+)

Chapter 3 7

Non-isolated drivers for a BJT: (a) single-transistor driver, (b) driver with a class B output stage

Fig. 3.6

TR

BJT

TR

BJT

TR

TR

1

2

3

C

(a ) (b )

C

(+)(+)

(-)

(-)

Chapter 3 8

Antisaturation Baker’s clamp for a BJT

Fig. 3.7

D4

D0

D1 D2 D3

Chapter 3 9

Driver for a BJT with transformer isolation

Fig. 3.8

(+)

(-)

BJT

T R

T R 1

2

P T R

Chapter 3 10

Driver for a BJT with transformer isolation

Fig. 3.9

(+)

(+ ) (+)

(+)

BJT

(+ )

(-)

(a)

(b)

Bi

ON

OFF

t

Chapter 3 11

Gate drive for a power MOSFET with a high-current TTL clock driver

Fig. 3.10

MOSFET

CD

(+)

Chapter 3 12

Driver for a power MOSFET with transformer isolation

Fig. 3.11

MOSFET

PTR

AM

D

Chapter 3 13

Driver for a power MOSFET with optical isolation

Fig. 3.12

( -)

(+ ) (+ )

AMP L

M O S F E T

( -)

(+ )

(+ )

(-)

Chapter 3 14

SCR crowbar for overcurrent protection of a power electronic converter

Fig. 3.13

SOURC ESUPPLY

CIRCUITCONTROL

CONVERTERAND LOAD

SCR

(+ )

(-)

R

Chapter 3 15

Totem-pole arrangement of two switches in a leg of a bridge topology

Fig. 3.14

R

(+ )

(- )

Chapter 3 16

BJT-based chopper with an RC snubber: (a) circuit diagram, (b) equivalent circuit in the off state

Fig. 3.15

i

vL

i L

V i

snR C sn

vCE

BJT

ii

vo IoD

(a )

i

vL

i L

V i

snR C sn

vCE ii

vo I

(b )

o - i iIo

Chapter 3 17

Voltage and current waveforms in the chopper of Fig. 3.15: (a) without snubber, (b) with snubber

Fig. 3.16

Io

VCE,piC0

Io ii

0 t0

vCE

(b)

Vi

t

VCE,p

0 t0

(a)

=

vCE

0

iC iit

Vi

Chapter 3 18

Switching trajectories of the BJT of Fig. 3.15: chopper iof Fig. 3.15: (a) without snubber, (b) with snubber

Fig. 3.17

Vi

SOA

Io

iC

vCE0

0 VCE,p

VCE,p

(a)0

Io

(b)

SOA

vCEVi

0

iC

Chapter 3 19

Snubbers for: (a) power diode, (b) SCR

Fig. 3.18

(a ) (b )

Chapter 3 20

GTO with turn-on and turn-off snubbers

Fig. 3.19

TUR N -O F FS N U B B E R

TUR N -O NS N U B B E R

i

i

i

v

Chapter 3 21

Combined on-and-off snubber for a transistor

Fig. 3.20

ii

iC

v CE

Chapter 3 22

Snubber for transistors in bridge converters: (a) RC, (b) RCD, (c) charge and discharge RCD, (d) discharge-suppressing RCD

Fig. 3.21

(a) (b)

(c) (d)

Chapter 3 23

Turn-off capacitive snubber with passive energy recovery

Fig. 3.22

Chapter 3 24

Turn-off capacitive snubber for a GTO with active energy recovery

Fig 3.23

Chapter 3 25

TABLE 3.1 Comparison of Thermal and Electrical Quantities

______________________________________________________________________________

Thermal Quantity Electrical Quantity ______________________________________________________________________________

Amount of heat (energy), Q (J) Electric charge, Q (C)

Heat current (power), P (W) Electric current, I (A)

Temperature, Θ (oK) Electric voltage, V (V)

Thermal resistance, RΘ (oK/W) Electric resistance, R (Ω)

Thermal capacity, CΘ (J/ oK) Electric capacitance, C (F)

Thermal time constant, 𝜏Θ = 𝑅Θ𝐶Θ (s) Electrical time constant, 𝜏= 𝑅𝐶 (s)

______________________________________________________________________________

Chapter 3 26

Power diode with a heat sink: (a) physical arrangement, (b) thermal equivalent circuit

Fig. 3.24

HEAT SINK

CAB LE

SEM ICO NDU CTOR

O

R S A

OR C S

OR J C

OC S

OC C

OC J

O J

O A

(a ) (b )

CASE WAF ER

P

O C

O S

l

Chapter 3 27

Block diagram of an adjustable-speed ac drive

Fig. 3.25

MO TO RIN VER TE R

C O N TR O L LERD S P

S Y S TE M RE FE RE NC ES PE E D S IGNA L

C URRE NT S IGNA LS

C URRE NTS ENS ORS

S PE E D S E NS OR

REF ERE NC E C URRENT SIGNALS

S PE E D S IGNA L

(+ )

(- )

C R A

C R

C R

B

C

LOAD